1. Technical Field
The present invention relates to a winding device for a stringed instrument such as a guitar, and relates to a manufacturing method therefore, and more particularly, the present invention relates to a technique for decreasing backlash of gears by preventing the generation of play in a worm gear and a bearing.
2. Background Art
FIG. 9 shows an example of a peg for a conventional classical guitar. As shown in this figure, a worm gear 3 having a knob 2, fixed to one end thereof, is rotatably supported on a main body 1 which is mounted to the guitar head. A worm wheel 4 meshing with the worm gear 3 is rotatably supported on the main body 1, and a winding shaft 5 which is coaxial with respect to the worm wheel 4 is mounted to the worm wheel 4 by a screw 6.
An ordinary steel plate is press molded and a plurality of bearings 7 are formed so as to be bent at an angle substantially equal to 90 degrees and is erected on the main body 1. The side of the shaft receiving portion is open so as to have a U-shaped recessed portion 7a. Grooves 3a which are formed in both end portions of the worm gear 3 engage with the recessed portion 7a and thereby support both end portions of the worm gear 3.
In addition, the wall portion of the worm gear 3 is nipped from both sides by two bearings 7 and 7, and hence resistance is given to the rotation of the worm gear 3 and this thus prevents rotation in the reverse direction (rotation causing loosening of the string). In the PEG, a string is wound on the winding surface 5a of the winding shaft 5, and the tuning of the stringed instrument is performed by rotating the knob 2 so that the string is wound or unwound.
However, in the PEG described in the foregoing, the backlash of the worm gear 3 and the worm wheel 4 is large. Furthermore, because the backlash gradually increases as the instrument is used, tuning becomes more difficult, and this may cause decreased performance.
That is to say, the side of the bearing 7 of the peg described in the foregoing is open, and thus its assembly is simple. However, in order to achieve this simple assembly, a large clearance must be provided between the worm gear 3 and the worm wheel 4, and the worm gear 3 is movable with respect to the worm wheel 4 according to the size of the clearance. As a result, the backlash between the worm gear 3 and the worm wheel 4 is large. Therefore, when the knob 2 is rotated by a small amount, the winding shaft does not rotate, and therefore fine tuning is difficult.
Furthermore, when the worm gear 3 as viewed from the side shown in FIG. 9 is rotated in a clockwise direction, the moment of the clockwise rotation having a center at the point P shown in FIG. 3 is added to the worm gear 3, and thus the worm gear 3 moves to the worm wheel 4 side. As a result, the seizure of teeth surfaces of both the worm gear 3 and the worm wheel 4 cause the teeth surfaces to wear and the backlash of the gears is even larger. Furthermore, in the peg described above, since the bearing 7 is formed of a ordinary steel plate which is low in strength, and also since the side of the bearing 7 is open, less of the wall portions can be supported than in comparison with the bearing of a round hole.
On the other hand, in consideration of bearing manufacturing error and ease of assembly, the grooves 3a of the worm gear 3 are made wider than the thickness of the bearing 7. As a result, due to the thrust load received from the worm gear 3, the bearings 7 and 7 which initially nipped the grooves 3a and 3a of the worm gear 3 from both sides, are deformed and open up. Consequently, the worm gear 3 also becomes movable in the thrust direction (axial direction). In a case in which a play is formed in the thrust direction, even when the worm gear 3 is rotated, it continues to idle until the groove 3a comes into contact with the bearing 7. Thus, the play in rotating the knob 2 is large, and tuning is extremely difficult.
Furthermore, when there is play at the worm gear 3 and the bearing 7 and the worm gear 3 is in a free state, the vibrations of the string may be transmitted to the worm gear 3, thereby causing an unusual noise during performance. The worm gear 3 rotates in the opposite direction due to the vibrations, and thus the notes become out of tune.
If the bearing is made so as to have a round hole, the worm gear 3 is prevented from moving in the direction of the worm wheel 4, and the problem of the large backlash as well as the problem that the backlash is increased due to the wear of the teeth surfaces are solved. However, although the strength of the bearing is increased because it is made to have a round hole, this alone does not sufficiently prevent transformation caused when the worm gear receives the thrust load. Accordingly, the problems of the generation of play due to the deformation of the bearing and the generation of unusual noises caused by this deformation, and of reverse rotation of the worm gear, remain unsolved.
In an effort to solve these problems, a peg is provided in which the main body and the bearing are formed separately and both parts are joined together by a welding or calking process. In this type of peg, each of the bearings is completely nipped at both sides using the flange, the washer, and the screw formed on the worm gear. In this type of peg, the thrust load in all directions is supported on a pair of bearings, and thus the resistance of transformation of the bearing is high. However, in this bearing, it is necessary to provide many parts in order to nip the respective bearings, and it is also necessary to carry out a calking process for preventing disengagement of the worm gear. Thus, there is a problem in that the number of processes to be carried out in assembly is increased.
In addition, examples of the peg which has been integrally formed by press molding the main body and the bearing, include those in which a ring is rotatably supported at one end of the worm gear, and a screw which is formed at the outer periphery of the ring is screwed together with a screw formed at the inner periphery of the bearing. In the peg having this type of structure, the ring is moved and the worm end surface of the worm gear is pressed with force, and thus the bearing can be secured to the worm gear so as to open to the outer side, and the play of the bearing and the worm gear in the thrust direction is eliminated. In addition, there is also an example in which a screw is formed on a shaft of a worm gear and a bearing is secured to the worm gear with a ring which engages with the screw. However, in this type of peg as well, the number of complicated parts is increased, and the manufacturing cost is relatively high.
An object of the invention is to provide, without significantly increasing the manufacturing cost, a peg in which the deformation of the bearing in the thrust direction is controlled, the play of the worm gear and the bearing in the thrust direction is eliminated, and accordingly, tuning is carried out easily, and problems of the generation of unusual noises and reverse rotation of the worm gear do not occur.